Topic 3 – Vector Control Strategies : What Are Our Strategies To Prevent Dengue & Zika

Topic 3 – Vector Control Strategies : What Are Our Strategies To Prevent Dengue & Zika


Assalamualaikum and good day everyone.
I’m Noraida Hashim, Dengue and zika posed great danger to human. Eventhough dengue vaccine has been developed, in many countries it might be too late as the vaccine usage still need an approval before it can be applied. Therefore, vector control is the main method to combat dengue and zika. In previous video, you’ve learn about dengue and zika vectors, the Aedes mosquitoes; Aedes aegypti and Aedes albopictus Now, in this video, we are going to learn another important topic in Dengue and Zika, which is the vector control strategies In this video, you will be exposed to various methods currently used to control the mosquito vectors particularly the container breeders such as Aedes. After you finish watching this video, we expect you to be able to : Explain how mosquito population monitoring and surveillance is done You should be able to describe the common and current methods used to control dengue and zika vectors And… You should be able to suggest integrated approach in controlling dengue and zika vectors. In trying to achieve those learning outcomes, we are going to cover a few main topics. Aedes mosquito attractants, Vector monitoring and surveillance, Control methods As you already learn in previous video, Dengue and Zika viruses are transmitted from one to another human through the bites of Aedes mosquitoes; Aedes aegypti and Aedes albopictus. Female mosquitoes bite to acquire blood which contain nutrients necessary for eggs development. Several factors were identified as attractant for mosquitoes to bites. They are: Aedes and other mosquitoes were found to be attracted to dark colour such as black. People wearing dark colour cloth were bitten more by mosquitoes compared to people wearing light colour cloth. They also attracted to carbon dioxide exhaled by human and animals Body heat also was found to lead mosquitoes to human Body odour from sweat due to bacteria activities in combination with body heat attract more mosquitoes to the host Light also was found to attract host seeking or blood -seeking females These information are important as it provide us advantage to develop and plan mosquito monitoring and control. Mosquito monitoring and surveillance are important as it will provide us the update on the population abundance and dynamics in the concern areas.
Usually monitoring and surveillance are done to determine when to start control efforts or to determined whether the control methods used effective in reducing Aedes population in outbreak area. For Aedes mosquitoes, several methods are commonly used to monitor the population. The first method is using ovitrap Ovitrap is a device used to trap Aedes mosquito eggs and larvae. It is an economical method and easy to operate. An ovitrap consisted of black container made of plastic or tin The black container will be ¾ filled with declorinated or seasoned tap water water and will be provided with oviposititon subtract made of hard board paddle. The gravid Aedes mosquitoes will lay eggs in the ovitrap Usually, the ovitrap will be placed in strategic areas such as in bushes, around house compound and in the house for 5 to 6 days. After that, observation will be made whether the ovitrap harbour Aedes larvae. The paddle will be brought back to laboratory for observation and egg counting under stereomicroscope. Human volunteers expose their legs for mosquitoes to land in Human landing catch method. This method is used to capture blood seeking female mosquitoes. The landed mosquito will be captured before it has opportunity to bite. Sometime, animal such as cattle is used instead of human. Backpack aspirator usually used to collect resting adult mosquitoes in the house or under foliage of vegetation. Light trap in combination with attractant such as carbon dioxide or other chemical cues was used to capture adults Although light trap widely used to trap adult mosquitoes, in comparison with human landing catch and aspirator, this method was proven ineffective to capture Aedes aegypti and Aedes albopictus as both are diurnal insect. All the trapping methods usually will capture adult’s mosquitoes of various species. Therefore, in addition to Aedes mosquito population, the surveyor also will gain information such as other species of mosquitoes that occur in the study area. Larval and pupal surveys usually conducted to search and destroy the breeding sites of Aedes and other mosquito’s species. Larval and pupal survey usually done by officers or personnel from vector unit, Ministry of Health. During survey the responsible officers will visit from house to house inspected around around and inside the house looking for Aedes breeding sites. As Aedes aegypti and Aedes albopictus are container breeders and they need stagnant and clear water to lay eggs. They can easily utilize various natural and artificial containers either outside or inside the house. Rainwater accumulated in discarded containers can become their breeding sites. Therefore, it is important for the search and destroys team to focus their efforts on searching the breeding sites inside and around the house compound. Usually, breeding sites found will be recorded for future reference and then destroyed. Sometimes, the larvae and pupae found will be brought back to laboratory for further study. There are several methods can be use to control Aedes mosquitoes. The control methods are divided into: Biological control, Chemical control
Environment management and sanitation In Biological control Using of MICROBIAL agent or pathogen especially bacteria has shown to be effective in the control of mosquito immatures. For example, Bacillus thurigiensis H-14 was used for control of clean water breeders such as Aedes and Anopheles mosquitoes. Some fish especially indigenous species such as guppy and panchax can be integrated with other control approaches For example guppy was reared in pots containing water plants such as water lily and lotus. Giant mosquito, Toxorhynchites splendens have potential as biological control for Aedes mosquito particularly Aedes albopictus. This giant mosquito usually found inbreeding sites of Aedes albopictus in suburban and rural areas with high vegetation. Toxorhynchites larvae predated on other mosquitoes larvae including Aedes albopictus and Aedes aegypti. Chemical control or pesticides consisted of larvicides and adulticides. Applications of adulticides or larvicides are made after the presence of mosquitoes has been demonstrated by monitoring and surveillance procedures. Larvicides Temephos (ABATE) is conventional larvicide used to kill clean water breeders such as Aedes. Newer insecticidal larvicides including alpha-cypermethrin (FENDONA), fenitrothion, permethrin and cyfluthrin can be used in both clean and polluted water. Insect Growth Regulators (IGRs) including juvenile hormone mimics (JHs) and chitin synthesis inhibitors (CSIs) are effective with less environmental impact. Examples of juvenile hormone mimics are methoprene and pyriproxypen Examples of chitin synthesis inhibitors are diflurobenzuron and triflumuron Fogging is the most efficient method for control of vectors such adult Aedes mosquitoes. Only small amounts of adulticides were used in the process Conventional sprayer, reach insects less effectively when compared to ultra low volume, ULV technology. This is because conventional sprayers spray larger droplet sizes in between 100-200 microns, which don’t fully cover the whole area being sprayed. Apart from the droplet size they produce, manual sprayers can be very time consuming and labour intensive. Although motorized versions spray quicker, there are not suitable for indoor use, as they leave surfaces very wet and produce exhaust gases. Manual sprayers are ideal when you need to spray close up, in places such as patio areas and gardens. In Thermal Fogging, pesticides or disinfectants mixed with oil heats up to produce a very dense and visible fog formed of droplets of around 10 microns in size Thermal fogging is ideal for exterior use to disinfect, combat vector carriers and pests. This method of fogging is not suitable for applying in closed indoor spaces due to the exhaust gases they produce. Ultra Low Volume Fogging, works by compressing pesticides or disinfectants through a specially designed nozzle producing a fine cold mist or aerosol. Electric portable versions are particularly ideal for indoor applications as they don’t produce exhaust gases and are less noisy. These machines can apply both oil and water based solutions Conventional insecticidal adulticides spray include malathion (both fogging and ultra-low volume formulation), fenitrothion (fogging) and synergized pyrethrins (fogging/ULV). The table shows the formulation or insecticides for fogging and ULV Sumithion L-40-S – An organophosphate-pyrethroid diesel-based thermal fogging formulation for both indoor and outdoor usage. Possess both adulticidal and larvicidal activities. Resigen – a synergized pyrethroid formulation for indoor fogging (water-based) and outdoor ULV (diesel-based) spray;
possesses both adulticidal and larvicidal activities. Aqua-Resigen – A microencapsulated water-based synergized pyrethroid formulation for outdoor ULV spray. Pesgurad PS102 – a microemulsion water-based synergized pyrethroid formulation for synergized pyrethroid formulation for outdoor ULV spray. Pesguard FG161 – a pyrethroid mixture (d-tetramethrin + cyphenothrin) for outdoor ULV (adulticide) to control the mosquito and indoor thermal forging (adulticide and larvicide) to control both larvae and adults. For the fish spray organophosphate compounds and pyrethroid compounds have been studied with the aim of replacing chlorinated hydrocarbon insecticides (DDT). The use of water-based formulations with improved effectiveness and with less human hazard has also provided both larvicidal and adulticidal effects against mosquitoes. Overall, adulticide sprays are effective for short-term and are used in epidemic disease situations to control infective mosquitoes It is less effective as a long-term control measure. To control Aedes mosquitoes spraying is done during their active time which is before dusk and after dawn. Household insecticide products are widely used by householders especially in Southeast Asia Asia for the prevention of man-mosquito contact, indoor and outdoor. The Household insecticide products are: coils, aerosols, vaporizing mats, liquid vaporizers and oil liquid sprays The use of repellents is encourage to prevent mosquito bite. The most effective ingredients in repellent is DEET (diethyltoluamide). This formulation products
available in the market include aerosols rub-on-stick, lotion and soap. An efficient way to control mosquitoes is to find and eliminate their larval habitat. Source reduction should be the best approach for controlling container breeders such as Aedes aegypti and Aedes albopictus. Public education and diligence is the key to success of combating these vectors. Homeowners can take several steps to prevent mosquito breeding on their own property such as: Destroy or dispose of tin cans, old tires, buckets, unused plastic swimming pools or other containers that collect and hold water. Do not allow water to accumulate in the saucers of flowerpots, cemetery urns or in pet dishes for more than 2 days. Clean debris from rain gutters and remove any standing water under or around structures, or on flat roofs. Check around faucets and air conditioner units and repair leaks or eliminate puddles that remain for several days. Change the water in birdbaths and drink once a week. Stock ornamental pools with top feeding predacious fish.
Ornamental pools may be treated with biorational larvicides [Bacillus thuringiensis subsp. israelensis (Bti or S-methoprene (IGR) containing products] under certain circumstances. Eliminate standing water around animal watering troughs. Check for trapped water in plastic or canvas tarps used for cover things Check around construction sites Recently another method of larval control has become available. The LarvaSonic is an acoustic larvicide system Sound energy transmitted into water at the resonant frequency of the mosquito larvae air bladders instantly ruptures internal tissue and causes death. An efficient way to control mosquitoes is to find and eliminate their larval habitat. Source reduction should be the best approach for controlling container breeders such as Aedes aegypti and Aedes albopictus. As we all know, some mosquitoes are vectors for a number of diseases for example Aedes are vectors for Dengue, Chikungunya and Zika Culex vectors for Japanese encephalitis, filariasis Anopheles vectors for Malaria Mansonia vectors for Filariasis The most important issue is the control of the mosquitoes’ breeding places. And number one is of course the Cleanliness of the environment The knowledge, attitude as well as the practice of our citizens have improved but some community still lack the good practice. We feel that health education still play an important role in increasing awareness of the public Improper or illegal waste disposal/garbage dumping area This will of course increase the numbers of breeding sites for Aedes mosquitoes. So among the strategy that had been done by The Heath Ministry is via Communication for Behavioral impact (COMBI) which is as part of the social mobilization to encourage citizens to take care of their own housing area. We have a total of 151 active COMBI localities in Terengganu so far and we plan to increase this number and also to ensure these COMBI localities actively participate in controlling aedes and dengue eventually Resistance of mosquitoes towards certain insecticides We have problem of resistance of mosquitoes to certain insecticides as well due to certain factors So the state as well as district entomology unit always monitor this factor. and if there is such incidence happening, they will give appropriate advices to the district vector team to avoid prolonging the resistance or spreading the resistance to other areas We at the state vector control unit use these vector control SOP which includes number 1 is to to the Situational Analysis where we identify the area which is prone to the breeding of the mosquitoes and categorized them into 4 groups Outbreak area, Area with the presence of dengue cases Priority 1 areas (recent outbreak areas within 6 months, localities with cases within 6 months, areas with Aedes index (AI)>2.5%,
*AI: Percentage of houses/premises +ve for Aedes larvae Breteau index (BI)>5 %
*BI: number of positive containers per 100 houses inspected Container index (CI)>10%)
*Cl: percentage of water-holding containers infested with larvae or pupae. and finally is the High risk areas of the dengues transmission Executing Control and Preventive Activities We sometimes do preventive fogging in area with high breeding index Larvaciding activities at no man’s land (Unoccupied land) using integrated approach which is chemical and non chemical Routine Aedes inspection especially at the locality with dengue cases “Kempen Gotong Royong” or cleanliness activities involving the communities as well as at all health facilities in Terengganu and also covering 200m radius from the health facilities at least 4 times per year. Health Promotions Health promotion is done continuously via poster, individual advice, dengue talk, and exhibition. Cooperation with the media to educate the people and warn them if there is an increase in dengue case at their housing area We also utilize the social media (whatsapp, facebook) to convey the message through posters designed by our heath education unit Inter-agency participation in cleaning the housing area. Eg: COMBI J3K (community leaders), Pihak Berkuasa Tempatan (local authority) Working with the Ministry of education to ensure all schools are free from Aedes Share the information regarding dengue cases with other agencies to work hand in hand to reduce dengue cases Legislative action Will be taken according to findings when we check premises or during special aedes preventive operations (if we find breeding place) Issue compound under the Destruction of Disease-Bearing Act 1975, can bring fine a maximum of RM500 Basically, vector control is a continuous process along the year but it also depends on the situation. If there is an outbreak, the vector control is going to be different approach and in accordance with guideline to control dengue outbreak and also using integrated vector management. Factors that contribute to the failure of vector control we will categorize according to disease triad where we have the agent factors, host/community factors and environmental factors. Agents Factors Vector resistance to insecticides, Vector mutation Host/Community Factors Lack of knowledge Not aware of containers that can potentially become the breeding sites for Aedes mosquitoes Unaware that dengue can lead to death and there is no definitive treatment for dengue Unaware that the best practice to combat dengue is to prevent the breeding of the mosquitoes to stop the disease transmission Poor attitudes Not managing waste disposal properly at housing area Not permitting the health personals to do fogging at their houses Poor practice Not cleaning the house routinely Giving excuses when asked to clean their housing area No one take care of the no man’s land even though it is located in their housing area Environmental Factors Climate change (suitable for breeding) Man-made breeding ground (eg construction sites also contribute to breeding areas Generally, vector unit JKNT received a good cooperation especially from J3K, PBT, Government agencies and NGOs but in certain locality it is challenging to get cooperation from the society as some of them are being negligence regarding their house cleanliness and thinks other people will clean their house for them. What people need to know is that vector unit JKNT role is to ensure all kinds of vector borne disease is under control and not causing outbreak in the society but it need collaboration from all citizens and agencies to realize it. For example Every people need to check their house at least once a week just 10 minutes for each session to ensure there is no Aedes breeding site at their house both inside and outside. To get involve in the community to clean the housing area especially at no man’s land (gotong royong) Use aerosol to kill adult mosquitoes Be cooperative to the health staffs Take treatment early if having fever To ensure PBT collecting waste disposal according to schedule Mosquito control is divided into two areas of responsibility Individual, and public Most often it’s performed following the Integrated Mosquito Management concept. Integrated Mosquito Management is based on ecological, economic and social criteria and integrates multidisciplinary methodologies into pest management strategies that are practical and effective to protect public health and the environment and improve the quality of life. It is preferable to achieve simultaneous control of adult and larval stages so as to reduce the overall vector mosquito population and subsequently reduce or disrupt the diseases transmission. In the case of dengue vector control, such an approach is essential due to transovarial transmission of dengue virus in Ae. aegypti and Ae. albopictus. Integrated control of both chemical and biological agents against mosquitoes should be implemented for overall mosquito control approaches. The integration of Bacillus thurigiensis H-14 (Bti) and two commercial chemical insecticide formulations (Aqua Resigen or Pesguard PS102) in ULV formulation for the control of both adults and immature stages of Aedes aegpti, Aedes albopictus and Culex quinquefasciatus is an example of such an approach. You have watched this video, Now, can you explain how mosquito population monitoring and surveillance were done? Can you describe the common and current methods used to control dengue and zika vectors Can you describe the integrated approach to control dengue and zika vectors? I hope you have enjoyed this video and slide shows, and have gain knowledge on dengue and zika vectors. In the next video, you’re going to explore another interesting topic, which is Mosquito Immune Response. Thank you and See you later! bye

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